What caused the Barack Obama administration to begin investigating the Donald Trump campaign last summer has come into clearer focus following a string of congressional hearings on Russian interference in the presidential election.

It was then-CIA Director John O. Brennan, a close confidant of Mr. Obama’s, who provided the information — what he termed the “basis” — for the FBI to start the counterintelligence investigation last summer. Mr. Brennan served on the former president’s 2008 presidential campaign and in his White House.

Mr. Brennan told the House Intelligence Committee on May 23 that the intelligence community was picking up tidbits on Trump associates making contacts with Russians. Mr. Brennan did not name either the Russians or the Trump people. He indicated he did not know what was said…

…To this day, nearly a year after Mr. Brennan alerted the FBI, there has been no public official confirmation that Trump people coordinated with the Russians on hacking. Sen. Dianne Feinstein, California Democrat and Senate Intelligence Committee member, said earlier this month she has seen no evidence of collusion.

The Senate and House Intelligence committees are both investigating that charge.